Conventionally, color television monitors typically employ CRTs (cathode ray tubes). In recent years, however, television monitors employing liquid crystal displays have been put into practical use thanks to slimming-down and low power consumption achieved in modern display modules. The mainstream of display modules for use in television monitors and large-screen monitors is the TFT (thin-film transistor) LCDs (liquid crystal displays). In a TFT LCD, on one of the glass substrates constituting a display panel, scanning lines and signals lines, both connected to TFTs, are formed in a matrix-like formation, and input terminals for those scanning and signal lines are arranged in an edge portion of the glass substrate. In general, there are more signal lines than there are scanning lines, and therefore the input terminals for signal lines are arranged collectively in a longer-side edge portion of the glass substrate, and the input terminals for scanning lies are arranged collectively in a shorter-side edge portion of the glass substrate. The input terminals for signal lines are connected, by TAB (tape-automated bonding), to a source drive circuit board, and the input terminal for scanning lines are connected, by TAB, to a gate drive circuit board. These circuit boards feeds signals to the individual lines. Separately from the source and gate drive circuit boards, there is provided a control circuit board that is electrically connected to the individual drive circuit boards by flexible printed circuits.
On the rear-surface side of the display panel, there is arranged a backlight, which may be either of the side-lit type including a linear lamp arranged on an edge face of a light guide plate or of a direct-lit type including a light source arranged immediately behind the rear surface of the display panel. Display modules for use in notebook personal computers and compact portable terminals, where slimness counts, typically adopt side-lit backlights. On the other hand, display modules for use in liquid crystal television monitors and large-screen monitors, where high brightness counts, typically adopt direct-lit backlights. In a display module with a direct-lit backlight, on the rear-surface side of a display panel, a light source such as a plurality of fluorescent lamps is arranged so as to face the display panel, and, between the light source and the display panel, a diffuser plate, a dimmer plate, and the like are arranged. The florescent lamps are housed in a rear casing formed of, for example, aluminum. In a direct-lit backlight, the distance from the fluorescent lamps to the display panel needs to be adjusted so that the entire display area of the display panel is lit with light with uniform intensity and thus with uniform brightness. Accordingly, the smaller the number of fluorescent lamps, the greater distance needs to be secured therefrom to the display panel. As a result, compared with a side-lit type, a direct-lit backlight unit is thicker, with its rear casing protruding on the rear-surface side of the display panel. To efficiently feed the light from the fluorescent lamps to the display panel, various means are taken such as using the inner surface of the rear casing as a reflector plate or disposing a reflector plate between the rear casing and the fluorescent lamps.
FIG. 11 shows a rear perspective view of such a display module 100, which includes a support frame 104 for housing and supporting a display panel, a rear casing 105 formed of a metal, and a front frame 106 having an opening in the portion thereof corresponding to the display area. The support frame 104 having the display panel housed therein is sandwiched between the rear casing 105 and the front frame 106, and then stopper tags 107 provided in a peripheral portion of the front frame 106 are bent onto the rear casing 105. In this way, these components are assembled into a single unit. On the rear surface of the rear casing 105 is fitted a control circuit board, which is then covered with a protective casing 108. A flexible printed circuit 109 electrically connects together a source drive circuit board fitted on the display panel and the control circuit board fitted on the rear casing 105, and another flexible printed circuit 110 electrically connects together a gate drive circuit board and the control circuit board. In this way, the individual drive circuit boards are fed with signals from the control circuit board.
Conventionally, these flexible printed circuits 109 and 110 are not fixed but left free. However, in display modules for use in television monitors and large-screen monitors, as increasingly large screens and increasingly high resolutions are sought, the number of pixels increases, and thus the number of signal lines increases, making larger particularly the flexible printed circuit 109 that connects to the source drive circuit board. As a result, when the display module is handled, the flexible printed circuit 109 is prone to be caught at some edge or other, leading to imperfect connection or breakage of the flexible printed circuit 109.
The flexible printed circuits may be fixed to the rear casing with double-sided adhesive tape or the like. In that case, however, every time the display module 100 undergoes maintenance, the double-sided adhesive tape needs to be removed or replaced. This leads to poor serviceability.
Furthermore, with conventional flexible printed circuits, satisfactory shielding against EMI (electromagnetic interference) has not been achieved. The display module 100 for use in a television monitor has a large screen, and is required to offer high image quality. Thus, in its flexible printed circuit 109, which is now larger than ever to cope with the increased number of pixels, it is more important than ever to achieve shielding against EMI. An effective way for achieving that end is now being sought.
When this display module 100 is used in a display unit such as a liquid crystal television monitor or other monitor, the display module 100 is housed in a decorative casing formed of a resin. At this time, as shown in FIG. 12, the display module 100 is put in a lower case 101, is then fixed thereto with screws put through fitting holes 102 provided in opposite edges of the display module 100, and is then covered with an unillustrated upper casing. The upper and lower casings are fastened together with screws just outside the right and left, or upper and lower, edges of the display module 100. The fastening with screws here is achieved by the use of bosses 103 arranged at least one of the upper and lower casings.
In this way, the bosses 103 used to fasten the casings together are located at both ends of the display module 100. This makes the outer dimensions of the casings so much larger as the extra dimensions occupied by the bosses 103.